There are many applications in which it is desirable, or even imperative, to sterilize the objects being used. For example, the food industry requires that silverware, dishes, pots and other cooking utensils be sterilized. In addition, there is a requirement that pharmaceutical and medical devices also be sterilized. For example, scalpels and other medical instruments must all be sterilized prior to each use.
In other cases, there are single use applications, wherein the device to be sterilized is only used once before disposal. Items, such as needles used to draw blood, and syringes used for injections, must be sterilized prior to use. In addition to the medical field, there are similar requirements in the pharmaceutical industry. Filters, housings, and disposable components, such as bags, bioreactors and tubes, must be sterilized prior to use.
Sterilization can be performed in a number of ways. For example, sterilization using heat, such as autoclaving, is one common practice. In other embodiments, sterilization is performed by subjecting the object to radiation, such as gamma or beta radiation. Chemical reactions, such as those involving ethylene oxide, are another method used to sterilize a component. Often, the manufacturing process of these pharmaceutical components includes a sterilization step. Therefore, the manufacturer can guarantee customers that the selected component has undergone a sterilization procedure.
Recently, there has been a growing demand by pharmaceutical and medical device customers for independent verification that a device has been correctly processed during autoclaving, gamma sterilization, freezing, or shipping. Knowing that a device, such as a filter, bag, tube, or drug compound, has been processed correctly allows the customer to be more assured that the device can be used directly.
Typically, as described above, this assurance is provided with process engineering controls whereby a linear manufacturing sequence moves the device into and out of a process. However, there are various ways for the process to fail while still fulfilling the process controls. For instance, equipment performing the process, such as a gamma irradiator, may malfunction and not dose a filter correctly. Other devices may obscure the gamma rays, therefore reducing the dosage below the minimum level where bacteria may be killed.
Several attempts have been made to address this problem. For example, common to prepackaged medical devices, manufacturers use chemical color changing dyes to indicate a successful exposure to radiation.
Another method is a semiconductor component can be produced having minimal or limited protective coating on the substrate. In this case, gamma radiation penetrates the semiconductor package and affects the unprotected portion of the integrated circuit. The effect of the radiation may be to change a parameter of the circuit, such as threshold voltage or leakage current. The protected and unaffected portion of the component includes a sensing circuit that can determine any change in these parameters as a result of radiation. The user can then access this information, such as by using wireless or wired means.
However, this process requires that the operator understand the method and protocol for communication used by the device. For example, the operator must know what memory location within the device contains the information relevant to the radiation testing. In addition, this information may be stored in different locations and using different protocols, depending on the particular component and manufacturer.
Therefore, it would be beneficial if there were an independent method to confirm that a component had been properly sterilized which was simple to use and required no knowledge of the underlying circuitry. Such a method should determine whether the component was properly exposed to the elevated temperatures, depressed temperatures or radiation required to sterilize it. It would also be beneficial if there were a system that could be easily deployed and provide this confirmation without requiring the customer or user to perform difficult or cumbersome procedures.